1. Field of the Invention
The present invention relates to an integrated inductor structure and an integrated transformer structure, especially to a highly symmetric 8-shaped integrated inductor and integrated transformer.
2. Description of Related Art
Inductors and transformers are important elements in radio frequency integrated circuits to implement single-ended to differential signal conversion, signal coupling and impedance matching. As System-on-chips (SoC) become the mainstream of integrated circuits, integrated inductors and integrated transformers gradually substitute conventional discrete elements and are commonly applied to radio frequency integrated circuits. However, inductors and transformers in integrated circuits often take up large areas; therefore, it becomes an important issue to reduce the areas of inductors and transformers in integrated circuits without degrading element performances, such as inductance, quality factor (Q), and coupling coefficient (K).
FIG. 1 illustrates a structure of a conventional 8-shaped integrated inductor. An 8-shaped integrated inductor 100 comprises a spiral coil 110 and a spiral coil 120. The spiral coil 110 (120) comprises a metal segment 112 (122) and a metal segment 114 (124). The metal segment 112 (122) and the metal segment 114 (124) are connected by through structures at through positions. The through structures can be via structures or a via array. In operation, signals are inputted at one terminal 111 (or 121) of the 8-shaped integrated inductor 100 and outputted at the other terminal 121 (or 111). The 8-shaped integrated inductor 100 has an obvious drawback, that the spiral coil 110 or the spiral coil 120 itself has unsatisfactory symmetry, causing poor performances of the quality factor and the inductance of the 8-shaped integrated inductor 100. Moreover, the two terminals 111 and 121 of the 8-shaped integrated inductor 100 are distant from each other, such that the connection with differential elements in an integrated circuit becomes difficult (which becomes even more apparent as the numbers of turns of the spiral coils get greater).